*{
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: #000;
}

.loader {
  position: relative;
  width: 200px;
  height: 200px;
  overflow: hidden;
  -webkit-box-reflect: below 1px linear-gradient(transparent, #0005);
}

.loader:hover {
  background: #03e9f4;
  box-shadow: 0 0 5px #03e9f4,
              0 0 25px #03e9f4,
              0 0 50px #03e9f4,
              0 0 200px #03e9f4;
}

.loader span {
  position: absolute;
  display: block;
}

.loader span:nth-child(1){
  top: 0;
  left: -100%;
  width: 100%;
  height: 40px;
  background: linear-gradient(90deg, transparent, #03e9f4);
  animation: animate 1s linear infinite;
  animation-delay: 0s;
}

@keyframes animate {
  0% {
    left: -100%;
  }
  100% {
    left: 100%;
  }
}

.loader span:nth-child(2){
  right: 0;
  top: -100%;
  width: 40px;
  height: 100%;
  background: linear-gradient(180deg, transparent, #03e9f4);
  animation: animateTwo 1s linear infinite;
  animation-delay: 0.5s;
}

@keyframes animateTwo {
  0% {
    top: -100%;
  }
  100% {
    top: 100%;
  }
}

.loader span:nth-child(3){
  bottom: 0;
  left: -100%;
  width: 100%;
  height: 40px;
  background: linear-gradient(270deg, transparent, #03e9f4);
  animation: animateThree 1s linear infinite;
  animation-delay: 0s;
}

@keyframes animateThree {
  0% {
    left: 100%;
  }
  100% {
    left: -100%;
  }
}

.loader span:nth-child(4){
  bottom: 0;
  top: 100%;
  width: 40px;
  height: 100%;
  background: linear-gradient(0deg, transparent, #03e9f4);
  animation: animateFour 1s linear infinite;
  animation-delay: 0.5s;
}

@keyframes animateFour {
  0% {
    top: 100%;
  }
  100% {
    top: -100%;
  }
}